1. Field of the Invention
This invention relates to the field of endoscopic surgery. More specifically the invention relates to obtaining accurate positional information about an anatomical structure within a patient's body and using this information to accurately position endoscopic cameras and surgical instruments within the patient's body.
2. Description of the Prior Art
Systems have been developed to augment a human surgeon's ability to perform surgery on a patient by providing the surgeon with intraoperative images of anatomical structures within the patient's body. Typically, these systems comprise a surgeon specialized form of camera or medical telescope. Further, a class of these systems, which includes endoscopic and laparoscopic instruments, has reduced the invasive nature of many surgical procedures.
This class of systems has two salient characteristics in common: First, the surgeon using the system cannot directly manipulate the patient's anatomy with his fingers, and second, the surgeon cannot directly observe what he is doing. Instead, the surgeon must rely on instruments that can be inserted through a trocar or through a working channel of an endoscope. Often, since his hands and attention are fully occupied in performing the procedure, the surgeon must rely on an assistant to point the endoscopic camera while the surgery is performed.
To ameliorate the awkwardness of this arrangement, robotic augmentation devices have been developed for endoscopic surgery. One such device is described in detail in a copending application entitled "System and Method for Augmentation of Surgery" Ser. No. 07/714,816 filed Jun. 13, 1991 which is herein incorporated by reference.
Robotic augmentation devices can potentially greatly assist surgeons during an operation. Robotic devices do not fatigue. Potentially, they can position medical telescopes and surgical instruments very accurately and can perform precise repositioning and repetitive functions. However, in order for these advantages to be realized, a number of problems need to be solved. The surgeon still needs to determine what motions the robotic device is to make and requires a means to communicate with the computer controlling the robot. In a few cases, such as orthopaedic machining of bone or pre-planned excision of a tissue volume determined from preoperative medical images (such as CT or MRI scans), these motions may be pre-planned. However, in other cases, the surgeon needs to directly observe the patient's anatomy and interactively specify the motions to be made relative to anatomical features and the medical telescopes. In these cases, means of accurately locating anatomical features and instruments relative to the medical telescopes and to each other and of using this information to control the robotic augmentation aids are necessary.
A specialized robotic device for stepping a resectoscope through a preprogrammed sequence of cuts in thranurethral prostatectomies has been developed. However, this system does not address the problem of providing the surgeon with a convenient means of controlling the view available through an endoscopic device or of providing the surgeon with means of interactively manipulating surgical instruments in response to intraoperative imaging and other sensory information.
There has been one attempt to provide voice control of a flexible endoscope in which servomotors attached directly to the control knobs of a commercial flexible endoscope were activated in response to voice commands by the surgeon. Difficulties of this approach include: (a) the surgeon (or an assistant) must still determine which direction to deflect the endoscope tip to provide a desired view and, consequently, must keep track of the relationship between the endoscope tip and the anatomical structures being observed; (b) these corrections must be made continually, distracting the surgeon from more important matters; and (c) the use of voice commands for this purpose is subject to errors, potentially distracting to the surgeon, and may make the use of voice for communication between the surgeon and operating room personnel more difficult. Several research efforts are directed to providing improved mechanisms for flexible endoscopes. These devices do not, however, simplify the surgeon's problem of controlling the endoscopic camera to obtain a desired view, either by himself or by communicating with a skilled operator.
3. Statement of Problems with the Prior Art
Unfortunately, the medical telescopes which are used in minimally invasive surgery have limited fields of view. As a result, only a small part of the anatomical Feature hidden inside the patient's body can be viewed at a one time. Furthermore, surgical telescopes typically provide only a single vantage point at any one time and it is difficult to provide the desired view.
Normally, to compensate for this limited field of view, a surgical assistant operates the telescope, reorienting it to produce many views of the anatomical feature. While doing this, the assistant must continuously keep track of the relative orientation between the telescope and the patient's anatomy in order to be able to quickly and correctly aim the telescope at the surgeon's request. He or she must also correctly interpret the surgeon's desires, which are not always evident from the surgeon's verbal comments.
This creates a number of problems. Surgical procedures of this nature now require an additional highly-skilled person to assist the surgeon in manipulating the medical telescope because the surgeon is using both of his hands performing other tasks. The communication that is required between the surgeon and the assistant increases the potential for an error while performing the surgery. The surgeon (and assistant) have to develop and keep a mental image of the entire hidden anatomical feature because the telescope can not capture the full image of the feature. Many telescopes, whether flexible or rigid, provide an oblique view, i.e., the direction of view is not coincident with the main axis of the telescope. This further exacerbates the difficulties of correctly aiming the telescope to achieve a desired view and increases the likelihood that the surgeon or the assistant could misconstrue the image presented or lose the orientation of the telescope with respect to the anatomical feature. Human fatigue contributes to a degradation of positioning of the telescope and/or of the interpretation of the images that the telescope transmits.
Accordingly, there is a need for a way to obtain accurate and reliable information about the position and appearance of anatomical features hidden within a body. There also is a need for an apparatus to accurately position and orient surgical instruments and/or medical telescopes within a body and to provide accurate information about their position with respect to hidden anatomical features. Further, there is a need to provide a reliable and accurate interface between the surgeon and his surgical instruments so that he can accurately position these instruments with respect to an anatomical feature within a body without removing his hands from his instruments.